The present invention generally relates to semiconductor devices, and more particularly to a semiconductor device having a test circuit.
In the production process of a large scale integrated circuit (LSI), defects are inevitably introduced. For this reason, it is necessary to carry out a test so as to check whether or not the produced LSI is as originally designed.
The test times for the LSI can roughly be divided into test items belonging to a D.C. characteristic test and test items belonging to an A.C. characteristic test. The D.C. characteristic test is carried out to test the static characteristic of the LSI, and is used to test input and output buffers of the LSI which function as interface circuits for providing an interface between a logic circuit within the LSI and an external circuit or device to the LSI. For example, the D.C. characteristic test checks whether or not a rated current flows through the input and output buffers and whether or not a rated voltage is obtained at the input and output buffers. On the other hand, the A.C. characteristic test is carried out to test the dynamic characteristic of the LSI, and is used to test the total operation of the LSI including the input and output buffers and the logic circuit of the LSI. For example, the A.C. characteristic test checks the functions of the logic circuit, that is whether or not a predetermined operation is carried out in the logic circuit, and the operation speed of the logic circuit. Presently, the test data used for carrying out these tests are made by the user in the case of a semi-customized LSI, since the logic operation of the logic circuit within the LSI is unknown to the actual manufacturer of the LSI.
Recently, the integration density of the LSI is becoming higher and higher and the logic operation of the logic circuit within the LSI is becoming more complex. As a result, there is a problem in that the process of making the test data is becoming more complex and troublesome due to the complexity of the logic circuit. Furthermore, the logic operation of the logic circuit within the LSI is different among different LSIs, and there is a problem in that different test data must be made for the different LSIs.